I'm speaking from just my own personal experience........ Dynamites are good engines, but my cousin had one and it blew within two weeks of him owning it, not sure if it was just a faulty engine or what, but luckily he was still able to get a new one under warranty...... I've never owned an rb or sts, but out of those two from what I've read up on the rb is the better choice (however rb engines are very expensive)........ I've owned nothing but OS engines (besides stock engines from ae and losi) and I love them........ They are very easy to tune and hold a their tune just great......... I don't think you can go wrong with any of the engines you've chosen, guess its just gonna come down to what you think is best for you..........